The lithium-ion secondary battery (hereinafter sometimes referred to as “lithium battery”) has a characteristic that it has a higher energy density than other secondary batteries and can be operated at a high voltage. Therefore, it is used for information devices such as cellular phones as it can be easily reduced in size and weight; and nowadays there are increasing demands for the lithium-ion secondary battery to be used as a power source for large-scale apparatuses such as electric vehicles and hybrid vehicles.
The lithium-ion secondary battery has a cathode layer, an anode layer, and an electrolyte layer disposed therebetween. An electrolyte to be provided in the electrolyte layer is for example a non-aqueous liquid electrolyte or a solid electrolyte. If a liquid (hereinafter referred to as an “electrolytic solution”) is used as the electrolyte, it easily permeates into the cathode layer and the anode layer. Therefore, an interface can be easily formed between the electrolytic solution and active materials contained in the cathode layer and the anode layer, and the performance of the battery can be easily improved. However, since commonly used electrolytic solutions are flammable, it is necessary to mount a system to ensure safety. On the other hand, solid electrolytes are nonflammable, thus allowing simplification of the above system. As such, there has been suggested a lithium-ion secondary battery having a layer containing a solid electrolyte, which is nonflammable, (hereinafter, the layer is referred to as a “solid electrolyte layer”, and the battery is referred to as a “solid battery”).
As a technique related to such a solid battery, Patent Document 1 for example discloses a method of manufacturing a lithium battery, the method including the steps of: dispersing an active material into a solvent containing a lithium ion conducting binder, thereby preparing an active material slurry; dispersing sulfide solid electrolyte into a solvent containing a lithium ion conducting binder, thereby preparing a solid electrolyte slurry; dripping the active material slurry and the solid electrolyte slurry onto a substrate, adjusting the thickness of the slurries by a blade, and further heat-drying and peeling the slurries, thereby forming an active material sheet and a solid electrolyte sheet; sandwiching the solid electrolyte sheet by two active material sheets and further sandwiching the two active material sheets by two current collector sheets, thereby forming a laminated body; and performing vacuum hot-pressing on the laminated body at a temperature no less than the melting point of the lithium ion conducting binder.